Acromegaly

Acromegaly is a rare chronic endocrine disease which affects approximately 70 persons per million (Ben-Shlomo & Melmed, 2008) .The most common cause is a primary autonomous growth hormone (GH) secreting pituitary adenoma. Increased mortality is usually associated with cardiac hypertrophy, hypertension and congestive heart failure. The example I have chosen is from a case study. It is of a 21 year old male, with digital overgrowth (large hands), prognathism (extended jaw line) and diastema (a cleft between two teeth) 182 cm in height and 94 kgs his vitals were within normal range and the only additional abnormal findings were coarsening of facial features. Cardiovascular examination and abdominal examination were normal. ( Aparci et al, 2006) Lab results showed a GH and insulin like growth factor-1 (IGF-1) levels of 34ng/ml and 443ng/ml respectively, indicating Acromegaly. (Normal range is 0-1ng/ml and 116-358ng/ml) An EKG showed left ventricular hypertrophy which was confirmed with transthoracic echocardiography and a dynamic MRI showed a left sided macro adenoma of the pituitary. ( Aparci et al, 2006) He underwent surgical removal of the tumor without any pharmacological intervention and was followed up closely with a cardiologist. ( Aparci et al, 2006) GH is synthesized and has pulsatile secretion from the somatotroph cells of the anterior lobe of the pituitary gland. Its secretion is regulated by the hypothalamus which is stimulated by GH releasing hormone (GHRH) this causes an Inhibition by somatostatin so that circulating GH stimulates synthesis and secretion of insulin-like growth factor 1 (IGF-1) from the liver. IGF-1 inhibits GH secretion at the pituitary and hypothalamus level creating a negative feedback loop. Symptoms are related to both excess of GH and IGF-1 secretion and to the expanding pituitary mass. (ARUP Consult, n.d) Both GH is partly regulated by a ‘short’ feedback loop i.e. it can feedback directly on the hypothalamus to inhibit its own release. The GH-stimulated release of IGFs from the liver also has important feedback effects on the control of GH. With a GH secreting adenoma, normal patterns of GH secretion are altered and become unpredictable. Even a slight elevation of GH can increase IGF-1 production which stimulates growth. For adults the epiphysis of the bones has sealed so long bone growth cannot occur and as a result there is connective tissue proliferation which causes changes in the bony proportions and bony proliferation thickening articulating surfaces of the joint spaces by the formation of osteophytes. This causes arthritic changes including pain and reduced mobility of the larger joints and the vertebrae. Excess GH also affects the kidney tubules by altering the phosphate reabsorption. This increases leading to mild hypephosphatemia. The metabolic effect of GH causes impaired carbohydrate tolerance and an increased metabolic rate. Peripheral glucose uptake is inhibited causing hyperglycemia and this goes along with hepatic glucose production, insulin resistance and compensatory over production of insulin. Approximately one third of people with Acromegaly develop glucose intolerance and half develop type 2 diabetes (Ben-Shlomo & Melmed, 2008). There are 3 types of medication that can be used in the treatment of Acromegaly: Somatostatin analogues (SSAs). The drugs octreotide (Sandostatin, Sandostatin LAR) and lanreotide (Somatuline Depot) are synthetic versions of the brain hormone somatostatin — growth hormone release-inhibiting hormone. They can decrease growth hormone levels by blocking the pituitary gland's excess production. Growth hormone receptor antagonists (GHRAs). The medication pegvisomant (Somavert) blocks the effect of growth hormone on body tissues. Dopamine agonists. Cabergoline (Dostinex) and bromocriptine (Parlodel) reduce growth hormone production and shrink tumors ( Mayo clinic, 2010) Aparci M; Kardesoglu E; Oezmen N; Cebeci BS; Uz O; Demiralp E.(2006) Acromegaly cardiomyopathy of a young patient at initial stage: a case report. Internet Journal of Cardiology (INTERNET J CARDIOL), 3(2). Retrieved from Cinahl Plus with full text. ARUP Consult(n.d) retrieved from http://www.arupconsult.com/Topics/Acromegaly.html Ben-Shlomo, A & Melmed,S (2008) Acromegaly . Endocrinol Metab Clin North Am.37(1).101-122 Mayo Clinic (2010) retrieved from http://www.mayoclinic.com/health/acromegaly/DS00478/DSECTION=treatments-and-drugs McCance, K.L., and Huether, S.E., (2010) Pathophysiology: The biologic basis for disease in adults and children, (6th ed) St Louis, Mo. Mosby Elsevier.